HEARING THRESHOLDS, THRESHOLD REPEATABILITY, AND ATTENUATION VALUES FOR PASSIVE NOISE-REDUCING EARPHONE ENCLOSURES

Passive noise-reducing earphone enclosures contain a supra-aural earph one mounted in a plastic dome. These enclosures are used to prevent th e elevation of hearing thresholds due to masking from high levels of a mbient noise. This research determined normal hearing threshold levels , threshold repeatability, and attenuation values for an Audiocup, Aur aldome II, AudioMate, and Madsen ME-70 enclosure. In Study I hearing t hresholds were obtained for 30 normally hearing adults from 500 to 600 0 Hz in four test sessions for each enclosure and a supra-aural earpho ne attached to a headband. The hearing thresholds and repeatability fo r the Audiocup and Auraldome were similar but the thresholds were high er and repeatability was poorer for the AudioMate and Madsen ME-70 com pared with the supra-aural earphone. In Study II real-ear attenuation values were obtained for each enclosure using 24 normally hearing subj ects. The Audiocup and Auraldome II provided less low-frequency attenu ation compared with the AudioMate and Madsen ME-70. The findings were related to the coupling of the supra-aural earphone in each enclosure to the ear and the coupling of each enclosure to the head. If an enclo sure is used as an alternative to a supra-aural earphone for hearing t esting in high ambient noise environments, hearing thresholds and thre shold repeatability should be similar to a supra-aural earphone, and t he enclosures should provide adequate attenuation of ambient noise. Si nce none of the enclosures met all of theses requirements, their use i s not recommended for hearing testing.